1. Field of the Invention
The present invention relates to blood warming apparatus and, more particularly, to apparatus for mechanically and rapidly admixing blood products at a storage temperature with a heated saline solution to produce a transfusable mixture without significant hemolysis at a rate commensurate with transfusion equipment and at a temperature within an acceptable range to avoid hypothermia.
2. Related Prior Art
The management of massive blood loss resulting from trauma or surgery necessitates rapid transfusion capability. In order to avoid the deleterious effects of hypothermia, it is necessary to warm blood from it's normal storage temperature of approximately 4.degree. C. prior to transfusion . Currently accepted blood warmers utilize passive heat transfer via dry warming panels or coils in a water bath. These warmers cannot adequately warm blood at flow gates exceeding 500 ml/minute. This slow warming rate represents the rate-limiting step in rapid transfusion. Other methods of blood warming which have been suggested include microwave ovens, which are considered to cause unacceptable hemolysis; blood bag emersion which is slow and not completely clinically tested; and, an extracorporeal heat exchanger which utilizes expensive equipment and has not been completely clinically studied.
Erythrocyte incubation studies have shown that prolonged exposure to temperatures greater than 48.degree. C. results in hemolysis and increased erythrocyte osmotic fragility. These results have been applied to the design of currently available blood warmers. Accordingly, heat source temperatures below 40.degree. C. are used which results in a slow transference of heat and dictates maximal blood warmer flow rates of less than 500 ml/minute. Because of these relatively low flow rates, blood warmer use in the emergent setting is often stopped just when a patient's transfusion requirement increases to the point where warming becomes most valuable. A typical state of the art blood warmer is sold under the trademark "INFUSER 37" by C. R. Bard, Inc. of Billerica, Mass. This blood warmer requires a heat exchanger wherein the heating water temperature is 40.degree. C. at a minimum flow rate of 10 1/minute.